Last week I had new fillings for my two incisors because the old ones were filled around 10 years ago and did not look well now. When the dentist was drilling the left incisor, I did not feel any pain. The dentist then took the X-ray and said I would need a root canal treatment as he spotted this tooth has died out and a shadow on the right bottom. He then drilled a little hole (here it hurt a little) at the back of the incisor and put some chemical (arsenic-free pulp devitalization) into the hole and asked me to go back in a few days for the canal root treatment.

I went back to him after a few days as the appointment was set, but I was so anxious that I was undecisive about the treatment. That incisor hurt once around 20 months ago, at that time another dentist took an X-ray and gave me some medicine and said “this tooth would only need root canal treatment if it hurts again.” So now it does not hurt for 20 months. I am not sure if it is really necessary to have the root canal treatment. Because this tooth is just fixed and looks ok now. After the root canal treatment the tooth would become so brittle that it would need a crown. I told the dentist I want to have a bit consideration. Now the dentist has cleared the chemicals he put in my tooth last time and fixed the little hole he drilled. Soon I started another worry as I read. I am worry if the chemical may leak without a complete root canal treatment and cause huge harm to my health in the future? I also consult another dentist for this matter, she said my tooth was not that serious to the extend that would require a root canal treatment yet.

I don't know what to do.
Here the X-rays are attached . I Would be very grateful for any of your experts’ insights and advice.